This is a continuation-in-part of U.S. patent application Ser. No. 09/217,221, filed Dec. 21, 1998 now abandoned.
The present invention relates generally to a light assembly, and more particularly, to an infrared light assembly that may be used on aircraft or other vehicles for landing, taxi mode, or search operations.
Infrared light sources may be useful in many different applications. For example, the military has extensively used infrared light sources for strategic military operations to provide night vision of terrain, people, objects, and targets. An infrared light source may be secured to an airplane, helicopter, or practically any other vehicle for use as a head light or a search light. In addition, an infrared light source may be used in a hand-held searchlight, or it may be mounted on a weapon such as a gun to provide an aiming light. In addition, infrared light sources may be used in many other military and non-military applications where visible light is not desired.
Infrared light sources utilized for exterior compatible lighting may be incandescent, electroluminescent, or IRLED. Incandescent sources may be filtered such that energy in the visible spectrum is not emitted. For example, category II Night Vision Imaging System (NVIS) searchlights may utilize black glass filtering systems. Other examples of category II lights include floodlights, fuel probe inspection lights, refueling lights, and landing lights.
Known infrared light sources may generate a substantial amount of heat. As the ambient temperature increases, the thermal signature increases. The halogen bulb energy spectrum encompasses the visible spectrum of radiation (380 to 770 nm) and the infrared spectrum of radiation (which is comprised of a near infrared region, 770 to 1400 nm, and a far infrared region, 1.4 to 1000 mm). Gen III goggle response limit is 930 nm. Thus, the wavelengths past 930 nm may not only be unnecessary, but also detrimental due to the high temperatures. This thermal radiation is in addition to the 200 watts which may be required to operate the halogen bulb.
The high temperatures generated by known infrared light sources may have many detrimental effects. The high temperatures may lead to material problems. The high temperatures may also lead to failure of the infrared light source (a searchlight, for example) and the surrounding components as well as the halogen bulb itself. In fact, the product life of known halogen bulb/black glass filtering systems may be rated at only approximately 50 hours. In addition, the high temperatures may cause lack of covertness. For instance, the high thermal signature may be detectable by forward looking infrared (FLIR), and the black glass filter does not filter all visible frequencies, i.e. the unit glows red.
Emitted infrared light may tend to diverge greatly and lose its intensity as it radiates from its source. As a result, known infrared light sources may require reflectors in order to produce a desired beam of infrared light. However, reflectors may increase the complexity and cost of the infrared light source.
In light of the shortcomings of known infrared light sources, a need exists for an improved infrared light assembly that is adapted to produce a high intensity, concentrated beam of infrared light. Another need exists for an improved method of dissipating the heat generated by an infrared light source so that it maintains peak emission. A need also exists for an infrared light assembly that requires less power to operate in order to minimize the thermal signature of the infrared light. Still another need exists for an infrared light assembly that has a longer product life.
Preferred embodiments of the present invention satisfy some or all of these needs. A preferred embodiment of a light assembly of the present invention may utilize an infrared light emitting diode, also well-known in the art as an “IR diode.” It should be noted that an IR light emitting diode has optical characteristics that differ from the characteristics of a “laser diode.” By its nature a laser light source produces coherent light which is highly collimated and directional. In contrast, IR light emitting diodes produce non-coherent light. In addition, IR light emitting diodes have a high refractive index and an isotropic spontaneous emission pattern.
A preferred embodiment of a light assembly of the present invention may also utilize heat dissipation means to maintain the infrared light emitting diode's temperature in order to prevent the frequency spectrum of the emitted light from shifting due to temperature effects, which is a characteristic of infrared light emitting diodes. Further, a preferred embodiment of a light assembly of the present invention may utilize an aspheric lens to provide a high intensity beam of infrared light.
A preferred embodiment of the present invention may emit a collimated beam of infrared light having a NVIS radiant intensity (NRI) greater than about 2:       N    ⁢                   ⁢    R    ⁢                   ⁢    I    =            ∫      450      930        ⁢                  G        ⁡                  (          λ          )                    ×              N        ⁡                  (          λ          )                    ×              ⅆ        λ            where: G(λ)=relative spectral response to NVIS    N(λ)=spectral radiant intensity of the light source (watt/steradian nanometer)    dλ=wavelength increment
Moreover, a preferred embodiment of the present invention may only require about 10 to 20 watts to operate. This may be a 90 to 95 percent power reduction as compared to known halogen bulb/black glass filter technology. The significant power reduction preferably minimizes the thermal signature of the infrared light. As a result, a preferred embodiment of the present invention may have a product life rated in the thousands of hours.
The present invention comprises a light assembly comprising: a thermally conductive housing, said housing having a bottom portion and a top portion, said housing defining a hollow; a thermally conductive base, said base located at said bottom portion; at least one light emitting diode disposed at said base, said light emitting diode adapted to emit infrared light, said infrared light being non-coherent and non-directional; and at least one aspheric lens connected to said top portion of said housing, said aspheric lens adapted to collimate infrared light to produce a beam of infrared light; wherein said infrared light emitted by said light emitting diode radiates through said hollow to said aspheric lens.
In addition to the novel features and advantages mentioned above, other objects and advantages of the present invention will be readily apparent from the following descriptions of the drawings and preferred embodiments.